In the absence of other stories, the British press is presently dominated by the reappearance of foot and mouth disease on a farm in the southeastern county of Surrey.

It looks as if this new outbreak has been contained, but British agriculture has still not recovered from the last epidemic in 2001, which was badly handled by the government and which alienated rural communities even more than the ban on fox-hunting.

Experts have traced the virus to the nearby research laboratories at Pirbright, which are shared by the government’s Institute of Animal Health and a private American corporation working in the same field, Merial. Sabotage has not been ruled out.

The fact that Merial is American has been featured prominently in the reporting of the story, even though, as I write, there is no evidence that the company has been negligent. Angry and frightened farmers are quick to identify a scapegoat. In this case, as in countless others, the default option is to blame America. Not unlike foot and mouth, anti-Americanism is an intellectual virus that, uncontained, quickly spreads throughout the body politic.

Take the military detention camp at Guantanamo Bay. The British have been told so many times by interested parties that prisoners there are tortured that they now firmly believe it. Britain’s government has never endorsed these tales of torture, but neither has it denied them. It has lent the criticisms credence by repeatedly calling for the camp to be closed, without explaining what else should be done with “enemy combatants,” or offering an alternative facility.

Britain has never publicly thanked American authorities for sharing the intelligence obtained from detainees at Guantanamo — even though this intelligence has been extremely valuable in preventing Al Qaeda from carrying out terrorist attacks in Britain and elsewhere.

The few British citizens in Guantanamo were released long ago, but five detainees from various Middle Eastern states who had been residents in Britain are still there. America offered to hand them back to the British, but the Blair government saw them as an embarrassment.

Now the new prime minister, Gordon Brown, has reversed his predecessor’s policy and this week formally requested the release of the five men, only one of whom no longer poses a threat according to the U.S. military. A letter from Foreign Secretary Miliband to Secretary of State Rice was published this week in the first in a series of moves aimed at appeasing Muslim opinion.

The problem here is not the detainees — the Americans will be as glad to see them go as the British are sorry to take over the task of keeping them under surveillance — but the accompanying mood music. Mr. Brown’s meeting with President Bush at Camp David last week was presented in Britain as a deliberate shift away from the Bush-Blair “band of brothers” to a cooler, more distant partnership allowing for open divergences and even disagreements. The change in policy of Guantanamo fits into this picture, for it is intended to put as much distance as possible between Mr. Brown and the more unpalatable aspects of the war on terror.

That war, however unmentionable in Mr. Brown’s circle, has not gone away. If the British are demanding the right to openly criticize the conduct of their American allies, they must expect the same in return. A senior U.S. intelligence official was quoted in the Washington Post this week in a devastating attack on the gradual British withdrawal from Iraq’s second city, Basra. “The British have basically been defeated in the south,” he said, claiming that the 500 troops left in the Basra Palace compound had been left “surrounded like cowboys and Indians.”

Military experts do not agree on the differing American and British methods, but one fact is undeniable: as U.S. troops in Iraq have surged to their highest-ever level of 162,000, the British have reduced their forces to an all-time low of just 5,500 troops. Despite the prime minister’s assurance to the president that Britain is not about to pull out of Basra, few Iraqis expect there to be more than a token of British presence in the city by this time next year.

Hence the 15,000 Iraqis who have worked for the British military and civilian authorities, and who now fear reprisals when the latter leave, hope to seek refuge in Britain. The official response to these Iraqis has been shamefully bureaucratic: they are directed to a Web site and told to apply for asylum like anybody else, with no guarantee that it will be granted. The Americans, by contrast, have looked after “their” Iraqis pretty well.

The reservoir of American goodwill built up by Tony Blair, and before him by Margaret Thatcher, could be drained quite quickly if Gordon Brown persists in pandering to anti-American attitudes. It is not as if there are no rivals for the Atlanticist prize.

Both the new, dynamic president of France, Nicolas Sarkozy, and the engaging chancellor of Germany, Angela Merkel, are already repairing the damage done by their predecessors and have no inhibitions about wooing Mr. Bush.

Luckily, the British and Americans still have a good deal of history in common. Mr. Sarkozy has unwittingly chosen to take his vacation in New Hampshire near the town of Wolfeboro, which is named after the General James Wolfe of Britain. It was Wolfe’s stunning victory at Quebec in 1759 — in which he was killed — that not only decided the fate of Canada, but also perhaps that of New England, too.

If the British had lost the Seven Years War, Americans today might speak French rather than English. I hope President Bush remembers that, however much he prefers the company of Mr. Sarkozy to the lugubrious Mr. Brown.